The prototype for the AtlasO Premier two-rail O Scale Offset-Side 2-Bay Hopper is based on cars used by the thousands to carry coal and aggregates. The Association of American Railroads (AAR) developed a standard design for 50-ton and 70-ton twin offset open hopper cars starting in the late 1920s. The design was modified in the mid 1930s, and through 1960 over 127,000 cars had been built to AAR specifications. Eastern coal carriers amassed the largest fleets - however, the twin offset hopper design was not limited to coal service, with ore and aggregates also being hauled. They could also be found operating in a wide range of services including unit coal trains, blocks of loaded cars destined to a large consignee, and single cars headed to smaller customers. This O Scale model features a detailed injection-molded body, fine decoration, metal wheels and metal knuckle couplers. This car has Kadee-compatible coupler mounting pads if you want to add your own body-mounted couplers. The Offset-Side 2-Bay Hopper is perfect for your steam and classic diesel-era train consists. Check out the entire line of AtlasO freight cars.